Functional reinforcing fillers modified with alkenylalkoxysilane and preparing method of the same

ABSTRACT

Disclosed are a functional reinforcing filler including inorganic particles surface-modified with an alkenylsilanol obtained by hydrolyzing an alkenylalkoxysilane compound, and a method for preparing the same. 
     Since the disclosed functional reinforcing filler has a functional group having a double bond, it has good reactivity for styrene-butadiene rubber and sulfur. Thus, when used as a functional reinforcing filler in the manufacture of rubber, it allows improvement of physical properties through adjustment of the addition amount of sulfur without additional use of the coupling agent. In addition, because of superior hydrolysis reactivity, the problem of alcohol can be solved and a rubber mixture with long scorch time can be prepared. In particular, when the functional reinforcing filler of the present invention is used in the manufacture of tires, improvement in modulus, tensile strength, rotational resistance and wet traction performance can be expected.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to Korean PatentApplication No. 10-2011-0041004 filed on Apr. 29, 2011, in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference in its entirety.

BACKGROUND

(a) Technical Field

The present invention relates to a functional reinforcing fillerincluding inorganic particles surface-modified with an alkenylsilanolobtained from hydrolysis of an alkenylalkoxysilane compound.

(b) Background Art

Since the mid-20th century, silanes having organic functional groupshave been widely used to enhance adhesion between silica and polymers orto improve compatibility. However, a silica-filled rubber compositiondoes not have a suitable reinforcing effect and an excellent improvementin physical properties can be attained only when a sulfur-containingcoupling agent such as 3-mercaptopropyltrimethoxysilane (MPTMS) is used.Further, the mercaptoalkyltrialkoxysilane coupling agent has offensiveodor and, when it is mixed with a polymer composition, processability isdegraded since the prevulcanization time is greatly reduced due to thepresence of highly reactive thiol (—SH) group.

In the early 1970s, bis(alkoxysilylalkyl)polysulfides[(RO)₃SiCH₂CH₂CH₂SxCH₂CH₂CH₂Si(OR)₃] were developed [U.S. Pat. No.3,842,111, U.S. Pat. No. 4,384,132, U.S. Pat. No. 4,507,490]. And, inthe early 1990s, Michelin announced the “green tires” usingbis(triethoxysilylpropyl)tetrasulfide (TESPT) [Eur. Patent EP 0501227,U.S. Pat. No. 5,227,425]. Since then, TESPT has been frequently used asa filler along with silica in order to improve the physical propertiesof a rubber composition. However, TESPT has a temperature restrictionwhen mixing it with a rubber composition. For instance, when it is mixedwith a rubber composition at high temperature, prevulcanization of therubber mixture occurs because of irreversible thermal cracking of thepolysulfane groups. Meanwhile, if the mixing is performed at lowtemperature, the alkoxy group of TESPT may not be completely hydrolyzed.According to Wolff, S., complete hydrolysis of TESPT is difficult to beattained at low temperature because of steric hindrance [Wolff, S.Kautsch. Cummi, Kunstst 1981, 34, 280]. As a result, the residual alkoxygroup exists in the molecule and hydrolysis occurs continuously evenafter mixing with the rubber composition. It decreases the life span ofthe rubber mixture as it is released as alcohol from inside the rubbermatrix

Thus, highly dispersible silica capable of minimizing the release ofalcohol and enhancing the dispersibility of silica is consistentlydeveloped by silica manufacturers [U.S. Pat. No. 0,176,852 A1]. However,the procedure of using TESPT and its product thereof cannot be free fromthe problem of alcohol release. At present, most of silica-containingrubbers use TESPT or MPTMS, and it is quite rare to use a silane havinga sulfur-free organic functional group, which allows less improvement inrubber properties, in a rubber mixture for a tire.

It is known that when an alkenylalkoxysilane having a sulfur-freeorganic functional group is mixed with a rubber together with silica,rubber properties can be improved by using a catalyst such asbutyllithium or peroxide [U.S. Pat. No. 0,019,554 A1]. However, in thatcase, coupling tends to occur with the silane coupling agent rather thanthe coupling between silica and rubber due to hydrolysis of the chlorineor alkoxy group of the silane, thus resulting in the formation ofpolysiloxane. This leads to insufficient improvement in the propertiesof the tire composite and inevitably leads to unfavorable processabilityand economic loss because of the need of additional use of additives inthe manufacture of rubber for tires.

In contrast, alkenylsilane, which is commonly used in the manufacture ofa rubber mixture, allows a long prevulcanization time when mixing with arubber composition and the mixing temperature is not particularlyrestricted. However, liquid alkenylsilanes, especially vinylsilane andallylsilane, have storage problems because of fast hydrolysis. Duringmixing with the rubber mixture, they are hydrolyzed quickly, leading tofast condensation with the coupling agent rather than thesilica-coupling agent-rubber coupling. Also, a larger amount of sulfuris required as compared to when a sulfur-containing coupling agent,e.g., MPTMS or TESPT, is used. That is to say, since the coupling agentis sulfur-free, solid sulfur or peroxide has to be added. Unless therubber mixture is mixed homogeneously, the desired improvement inphysical properties cannot be attained.

SUMMARY

The inventors of the present invention have worked to solve theaforesaid problems of the existing art. As a result, they have found outthat, by chemically treating the surface of inorganic particles with asulfur-free alkenylalkoxysilane compound instead of usingbis(triethoxysilylpropyl)tetrasulfide (TESPT) or3-mercaptopropyltrimethoxysilane (MPTMS), a hydrophobic, highlydispersible, a functional reinforcing filler having superiorcrosslinking reactivity and being easily miscible with rubber can beprepared.

The present invention is directed to providing_a functional reinforcingfiller and a method for preparing the same.

In one general aspect, the present invention provides a functionalreinforcing filler including inorganic particles surface-modified withan alkenylsilanol solution obtained by hydrolyzing analkenylalkoxysilane compound represented by Chemical Formula 1:R—SiX¹X²X³  (1)

Wherein R is C₂-C₁₈ alkenyl or C₅-C₁₈ cycloalkenyl, and each of X¹, X²and X³, which are the same or different, is C₁-C₁₈ alkyl, C₁-C₁₈ alkoxy,C₆-C₁₈ aryl or C₆-C₁₈ aromatic alkoxy, with the proviso that at leastone of X¹, X² and X³ is C₁-C₁₈ alkoxy or C₆-C₁₈ aromatic alkoxy.

In another general aspect, the present invention provides a method forpreparing a functional reinforcing filler, including: preparing analkenylsilanol solution by hydrolyzing the alkenylalkoxysilane compoundrepresented by Chemical Formula 1; preparing a suspension by mixing thealkenylsilanol solution with inorganic particles in one or more solventselected from alcohol and water; preparing molecular film coatedinorganic particles by removing the solvent from the suspension throughevaporation; and heating the molecular film coated inorganic particlesto induce dehydration condensation.

In another general aspect, the present invention provides a method forpreparing a functional reinforcing filler, including: preparing asuspension by mixing the alkenylalkoxysilane compound represented byChemical Formula 1 with inorganic particles in one or more solventselected from alcohol and water; removing the solvent from thesuspension through evaporation; and heating the inorganic particles toinduce dehydration condensation and thereby modifying the surface of theinorganic particles.

The above and other aspects and features of the present invention willbe described infra.

DETAILED DESCRIPTION

Hereinafter, reference will now be made in detail to various embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings and described below. While the invention will bedescribed in conjunction with exemplary embodiments, it will beunderstood that the present description is not intended to limit theinvention to those exemplary embodiments. On the contrary, the inventionis intended to cover not only the exemplary embodiments, but alsovarious alternatives, modifications, equivalents and other embodiments,which may be included within the spirit and scope of the invention asdefined by the appended claims.

The present invention provides a functional reinforcing fillercomprising inorganic particles surface-modified with an alkenylsilanolsolution obtained by hydrolyzing an alkenylalkoxysilane compoundrepresented by Chemical Formula 1:R—SiX¹X²X³  (1)

wherein R is C₂-C₁₈ alkenyl or C₅-C₁₈ cycloalkenyl, and each of X¹, X²and X³, which are the same or different, is C₁-C₁₈ alkyl, C₁-C₁₈ alkoxy,C₆-C₁₈ aryl or C₆-C₁₈ aromatic alkoxy, with the proviso that at leastone of X¹, X² and X³ is C₁-C₁₈ alkoxy or C₆-C₁₈ aromatic alkoxy.

R is C₂-C₁₈ alkenyl or C₅-C₁₈ cycloalkenyl. The number of carbon atomsof R may be in the aforesaid range since it is not easy to prepare analkenyl group having more than 18 carbon atoms and the processing timemay increase due to slow hydrolysis. More specifically, it may be C₂-C₁₀alkenyl.

Each of X¹, X² and X³ is C₁-C₁₈ alkyl, C₁-C₁₈ alkoxy, C₆-C₁₈ aryl orC₆-C₁₈ aromatic alkoxy, with the proviso that at least one of X¹, X² andX³ is C₁-C₁₈ alkoxy or C₆-C₁₈ aromatic alkoxy to allow conversion intoan alkenylsilanol via hydrolysis.

Particularly, the alkenylalkoxysilane compound may be one or morecompounds selected from vinyltrimethoxysilane (VTMS),allyltrimethoxysilane (ATMS), 5-hexenyltrimethoxysilane (HTMS),7-octenyltrimethoxysilane (OTMS),(bicyclo[2.2.1]hept-5-en-2-yl)trimethoxysilane (BCHTMS),vinyltriethoxysilane (VTES), allyltriethoxysilane (ATES),5-hexenyltriethoxysilane (HTES), 7-octenyltriethoxysilane (OTES) and(bicyclo[2.2.1]hept-5-en-2-yl)triethoxysilane (BCHTES). Mostspecifically, allyltrialkoxysilane may be used.

The inorganic particles may be one or more selected from silica, mica,talc, titanium oxide, zirconium oxide, tin oxide, iron oxide and zincoxide, although not being limited thereto. Specifically, one or moreselected from silica and mica may be used. And, the inorganic particlesmay have an average particle diameter 5 nm to 100 μm. When the averageparticle diameter is smaller than 5 nm, the cost is too high. And, whenit exceeds 100 μm, the performance of the elastomer as the reinforcingfiller may be degraded. Hence, the average particle diameter may bewithin the aforesaid range. And, the inorganic particles may have a BETsurface area of 50 to 1,000 m²/g. The silica may be one or more selectedfrom precipitated silica and colloidal silica. More specifically, one ormore selected from Zeosil (Rhodia), Hi-Sil (PPG Industries) and VN(Evonik) may be used. The precipitated silica may be prepared by variousmethods known in the art. As a specific example, it may be prepared froma solution of sodium silicate by acid precipitation.

Hereinafter, a method for preparing the functional reinforcing filler ofthe present invention will be described in detail.

[Preparation Method]

The functional reinforcing filler of the present invention comprisinginorganic particles surface-modified with an alkenylsilanol solutionobtained by hydrolyzing an alkenylalkoxysilane compound represented byChemical Formula 1 may be prepared by the following two preparationmethods:R—SiX¹X²X³  (1)

wherein R is C₂-C₁₈ alkenyl or C₅-C₁₈ cycloalkenyl, and each of X¹, X²and X³, which are the same or different, is C₁-C₁₈ alkyl, C₁-C₁₈ alkoxy,C₆-C₁₈ aryl or C₆-C₁₈ aromatic alkoxy, with the proviso that at leastone of X¹, X² and X³ is C₁-C₁₈ alkoxy or C₆-C₁₈ aromatic alkoxy.

[Preparation Method 1]

The functional reinforcing filler of the present invention may beprepared from a process comprising: a first step of preparing analkenylsilanol solution by hydrolyzing the alkenylalkoxysilane compoundrepresented by Chemical Formula 1; a second step of preparing asuspension by mixing the alkenylsilanol solution with inorganicparticles in one or more solvent selected from alcohol and water; athird step of preparing molecular film coated inorganic particles byremoving the solvent from the suspension through evaporation; and afourth step of heating the molecular film coated inorganic particles toinduce dehydration condensation.

In the first step, an organic acid that can be evaporated relativelyeasily or do not require neutralization may be used as an acid tohydrolyze the alkenylalkoxysilane compound. Specific examples includecarboxylic acids such as acetic acid, formic acid, butyric acid,palmitic acid, oxalic acid, tartaric acid, etc., ascorbic acid, uricacid, or the like, but are not limited thereto. The hydrolysis of thealkenylalkoxysilane compound may be performed at 0 to 100° C., morespecifically at 10 to 80° C. The reaction temperature may be differentdepending on the kind of reactants, e.g., organometallic compounds,acids and fillers, and solvents. And, the hydrolysis may be performed atpH 2.5 to 5.0. When the pH is below 2.5, formation of polysiloxane maybe accelerated due as the alkenylalkoxysilane is hydrolyzed quickly,thereby resulting in reduced reactivity with the surface of theinorganic particles. And, when the pH exceeds 5.0, alcohol may bereleased during mixing with the rubber composition because thehydrolysis occurs too slowly. Hence, the aforesaid pH range may bepreferred.

In the second step, the solvent used in the suspension may be one ormore solvent selected from alcohol and water. The alcohol may be C₁-C₁₀alcohol. Specifically, it may be selected from methanol, ethanol,propanol, butanol, pentanol, hexanol or phenol.

When preparing the suspension, a sulfur-containing coupling agent may beadditionally added. Specifically, the coupling agent may be asulfur-containing compound selected frombis[(trimethoxysilyl)propyl]tetrasulfide (TMSPT),bis[(triethoxysilyl)propyl]tetrasulfide (TESPT),3-mercaptopropyltrimethoxysilane (MPTMS) and3-mercaptopropyltriethoxysilane (MPTES).

In the third step, as the solvent included in the suspension evaporates,the silanol (Si—OH) group of the hydrolyzed alkenylsilanol thealkenylsilanol hydrolyzed is coated on the surface of the inorganicparticles via hydrogen bonding with the hydroxyl (M-OH) groups on thesurface of the inorganic particles, thus forming a molecular film.Later, when the molecular film is heated, M-O—Si covalent bonding isformed via dehydration condensation. Since the solvent is removed byevaporation, an additional neutralization or filtration process may beunnecessary. In this process, low-boiling-point alcohol may be removed.

In the fourth step, the dehydration condensation may be performed at100° C. or higher, specifically at 100 to 150° C., under an atmosphereor a pressure of 1 to 20 mmHg.

The alkenylalkoxysilane compound represented by Chemical Formula 1 maybe used in an amount of 1 to 20 parts by weight, specifically 3 to 15parts by weight, more specifically 5 to 15 parts by weight, based on 100parts by weight of the inorganic particles.

[Preparation Method 2]

Also, the functional reinforcing filler of the present invention may beprepared from a process comprising: preparing a suspension by mixing thealkenylalkoxysilane compound represented by Chemical Formula 1 withinorganic particles in one or more solvent selected from alcohol andwater under an acidic condition; removing the solvent from thesuspension through evaporation; and heating the inorganic particles toinduce dehydration condensation and thereby modifying the surface of theinorganic particles:

In the preparation method 2, unlike in the preparation method 1, thesurface of the inorganic particles is chemically modified while thealkenylalkoxysilane compound is hydrolyzed. However, the two preparationmethods have many things in common in that 1) the coated inorganicparticles are dehydration condensed after the alcohol and water areremoved by evaporation, 2) the prepared hydrophobic, highly dispersiblefunctional reinforcing filler does not release the alcohol component,and 3) the same reactants are used. In the preparation method 2, like inthe preparation method 1, a molecular film is formed on the surface ofthe inorganic particles via hydrogen bonding between the silanol (Si—OH)group of the hydrolyzed alkenylsilanol and the hydroxyl (M-OH) group onthe surface of the inorganic particles as the alcohol and water areevaporated. When the molecular film is heated, M-O—Si covalent bondingis formed via dehydration condensation. Since the alcohol and water areremoved by evaporation, an additional neutralization or filtrationprocess may be unnecessary. In this process, low-boiling-point alcoholmay be removed.

The alkenylalkoxysilane compound represented by Chemical Formula 1 maybe used in an amount of 1 to 20 parts by weight, specifically 3 to 15parts by weight, more specifically 5 to 15 parts by weight, based on 100parts by weight of the inorganic particles.

The acidic condition may be pH 2.5 to 5.0. Under this condition, thealkenylalkoxysilane compound is hydrolyzed to give a clear solution.When the pH is below 2.5, formation of polysiloxane may be accelerateddue as the alkenylalkoxysilane is hydrolyzed quickly, thereby resultingin reduced reactivity with the surface of the inorganic particles. And,when the pH exceeds 5.0, alcohol may be released during mixing with therubber composition because the hydrolysis occurs too slowly. Hence, theaforesaid pH range may be preferred. And, an organic acid that can beevaporated relatively easily or do not require neutralization may beused as an acid to prepare the acidic condition. Specific examplesinclude carboxylic acids such as acetic acid, formic acid, butyric acid,palmitic acid, oxalic acid, tartaric acid, etc., ascorbic acid, uricacid, or the like, but are not limited thereto.

The alcohol may be C₁-C₁₀ alcohol. Specifically, it may be selected frommethanol, ethanol, propyl alcohol, butanol, pentanol, hexanol or phenol.

When mixing the alkenylalkoxysilane compound with the inorganicparticles, the alcohol and water, a sulfur-containing coupling agent maybe additionally added. Specifically, the coupling agent may be asulfur-containing compound selected frombis[(trimethoxysilyl)propyl]tetrasulfide (TMSPT),bis[(triethoxysilyl)propyl]tetrasulfide (TESPT),3-mercaptopropyltrimethoxysilane (MPTMS) and3-mercaptopropyltriethoxysilane (MPTES).

The highly dispersible functional reinforcing filler of the presentinvention prepared by the preparation method 1 or 2 does not emitvolatile organic compounds (VOCs) because the alkenylalkoxysilane ishydrolyzed. The functional reinforcing filler of the present inventioncontains 0.1 wt % or more, specifically 0.1 to 20 wt %, of carbon basedon the total weight of the reinforcing filler.

Hereinafter, a rubber composition comprising the hydrophobic, highlydispersible functional reinforcing filler of the present invention willbe described.

[Rubber Composition]

The present invention is also directed to providing a rubber compositioncomprising the highly dispersible functional reinforcing filler. Todescribe in more detail, the rubber composition of the present inventioncomprises an elastomer as well as the hydrophobic, highly dispersiblefunctional reinforcing filler. It may further comprise one or moreadditive selected from an accelerator and a retardant.

In the rubber composition, the hydrophobic, highly dispersiblefunctional reinforcing filler may be used in an amount of 10 to 200parts by weight, more specifically 20 to 150 parts by weight, based on100 parts by weight of the elastomer.

The elastomer may be a thermoplastic or thermosetting elastomer.Specifically, one or more selected from a homopolymer comprisingconjugated diene monomers and a copolymer comprising a conjugated dienemonomer, a monovinyl aromatic monomer and a triene monomer may be used.

The elastomer may further comprise an organic rubber. The organic rubbermay comprise one or more selected from: a natural rubber (formed fromhomopolymerization of butadiene or its homologues or derivatives);1,4-polyisoprene, 3,4-polyisoprene, trans-1,4-polybutadiene,cis-1,4-polybutadiene or 1,2-polybutadiene; one or more ethylene-basedunsaturated copolymeric monomer comprising butadiene and its homologuesor derivatives; a butadiene-styrene copolymer using a butadiene isomer;polymers of isoprene, styrene and butadiene and various terpolymersthereof; an acrylonitrile-based copolymer and terpolymer rubbercomposition; and an isobutylene-based rubber.

Also, the elastomer may further comprise alkyd resin, natural oil,oil-modified alkyd resin, nylon, epoxide, thermoplastic polyester,unsaturated polyester, polycarbonate, or the like. More specifically,polyethylene, polypropylene, polybutylene, polystyrene,ethylene-propylene copolymer or terpolymer, polyoxymethylene and itscopolymer, polyurethane, nitrocellulose, phenol resin, polysulfiderubber, vinyl butyrate, vinyl chloride, vinyl acetate, cellulose acetateand butyrate, viscose rayon, cellulose, ethylene copolymer, wax,shellac, organic rubber, etc., may be used. However, the presentinvention is not limited thereto.

A non-limiting example of preparing a rubber composition using thefunctional reinforcing filler of the present invention is as follows.

A vulcanized rubber composition may be prepared by a process comprising:a step of mixing a curable elastomer with the hydrophobic, highlydispersible functional reinforcing filler, an accelerator and aretardant to form a vulcanizable elastomer composition; and a step ofcuring the vulcanizable elastomer composition by adding a curing agent.

The accelerator may be one or more selected from benzothiazole,benzothiazole sulfenamide, dithiocarbamate, thiopholine, thiourea,xanthate, thiuram sulfide, amine and dithiophosphate.

More specifically, the accelerator may comprise one or more selectedfrom: one or more benzothiazole selected from 2-mercaptobenzothiazole,zinc 2-mercaptobenzothiazole, 2,2′-dithiobisbenzothiazole,2-morpholinothiobenzothiazole, 2-(4-morpholinodithio)benzothiazole,2-(4-morpholinothio)benzothiazole,2-(4-morpholinothio)-5-methylbenzothiazole,2-(4-morpholinothio)-5-chlorobenzothiazole,2-(2,6-dimethyl-4-morpholinothio)-benzothiazole,2-(3,6-dimethyl-4-morpholinothio)benzothiazole, 2,2′-dibenzothiazoledisulfide and 2-mercaptobenzothiazyl disulfide);

one or more benzothiazole sulfenamide selected fromN-cyclohexyl-2-benzothiazole sulfenamide,N,N′-dicyclohexyl-2-benzothiazole sulfenamide,N,N-diethyl-2benzothiazole sulfenamide, N-t-butyl-2-benzothiazolesulfenamide, N,N-diisopropyl-2-benzothiazole sulfenamide,N-oxydiethylene-2-benzothiazole sulfenamide and N-oxydiethylenethiocarbamyl-N-oxydiethylene sulfenamide;

one or more dithiocarbamate selected from cadmiumdiethyldithiocarbamate, lead diamyldithiocarbamate, leaddimethyldithiocarbamate, zinc dimethyldithiocarbamate, zincdiethyldithiocarbamate, zinc diamyldithiocarbamate, zincdi-n-butyldithiocarbamate, zinc dimethylpentamethylene dithiocarbamate,bismuth dimethyldithiocarbamate, copper dimethyldithiocarbamate,selenium diethyldithiocarbamate, selenium dimethyldithiocarbamate,tellurium diethyldithiocarbamate, piperidinium pentamethylenedithiocarbamate, 2-benzothiazole-N,N-diethyldithiocarbamate anddimethylammonium dimethyldithiocarbamate;

one or more thiopholine selected from 4-mercaptomorpholine,4-mercapto-2,6-dimethylmorpholine, 4,4′-dithiomorpholine,4[(4-morpholinylthio)thixomethyl]morpholine, 2,6-dimethylmorpholinedisulfide, methylmorpholine disulfide, propyl 2,6-dimethyl morpholinedisulfide, alkyl morpholine disulfide and phenyl morpholine disulfide;

one or more thiourea selected from trimethylthiourea,1,3-dibutylthiourea, N,N′dibutylthiourea, 1,3-diethylthiourea,dimethylethylthiourea, diphenylthiourea and tetramethylthiourea;

one or more xanthate selected from sodium isopropylxanthate, zincisopropylxanthate and zinc dibutylxanthate;

one or more thiuram sulfide selected from tetramethylthiurammonosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide,tetrabutylthiuram disulfide, dipentamethylenethiuram tetrasulfide,tetrabenzylthiuram disulfide, dimethyldiphenylthiuram disulfide anddipentamethylenethiuram monosulfide;

one or more amine selected from cyclohexylethylamine, dibutylamine,heptaldehyde-aniline condensate, acetaldehyde-aniline condensate andguanidine, e.g., N,N′-diphenylguanidine, N,N′-di-o-tolylguanidine,o-tolylbiguanidine, N,N′,N″-triphenylguanidine and diarylguanidine; and

dithiophosphate.

Further, the retardant may be one or more amine selected fromN-(cyclohexylthio)phthalimide, phthalic anhydride, benzoic acid,salicylic acid, stearic acid, N-nitrosodiphenylamine, sodium acetate,aromatic sulfonamide, dioctyl phthalate and magnesium oxide. Morespecifically, the retardant may be one or more amine selected fromN-(cyclohexylthio)phthalimide, phthalic anhydride and aromaticsulfenamide.

In addition, the rubber composition may further comprise sulfur in orderto improve physical properties. Specifically, sulfur may be added in anamount of 0.1 to 10 parts by weight, more specifically 1 to 5 parts byweight.

Rubber prepared using the rubber composition including the functionalreinforcing filler of the present invention may have high tan δ at 0° C.and low tan δ at 60° C. Furthermore, the hydrophobic, highly dispersiblefunctional reinforcing filler of the present invention is capable ofimproving the processability and physical properties of rubber. Therubber prepared using the hydrophobic, highly dispersible functionalreinforcing filler of the present invention may have a scorch timeexceeding 14 minutes and a curing time less than 30 minutes (ASTMD5289-95). The compounded product may have a 300% modulus of at least5.0 MPa (ASTM D412-98a). The hydrophobic, highly dispersible functionalreinforcing filler of the present invention may be applied to themanufacture of a variety of rubber products, e.g., automotivedrive-belts, engine mounts, V-belts, conveyor belts, roller coatings,tires, components of tire (vehicle tire treads, subtreads, carcases,sidewalls, belt wedges, bead fillers and wire skim coats), shoe solematerials, packing rings, wire and cable sheaths, hoses, gaskets,sealing materials, or the like, so that the rubber products may haveexcellent tensile properties and dynamic properties.

EXAMPLES

The examples and experiments will now be described. The followingexamples and experiments are for illustrative purposes only and notintended to limit the scope of this invention.

Test Example 1 Hydrolysis of Alkenylalkoxysilane

100 parts by weight of a 1% acetic acid aqueous solution based on 100parts by weight of an alkenylalkoxysilane compound was added to acontainer including the alkenylalkoxysilane compound. Thus preparedsolution was stirred at 25° C. until all the hydrophobic alkoxy groupsof the alkenylalkoxysilane compound were converted into hydrophilichydroxyl groups to give a clear solution. Reaction time is shown inTable 1. The used organic alkoxysilane compounds werevinyltrimethoxysilane (VTMS), allyltrimethoxysilane (ATMS),7-octenyltrimethoxysilane (OTMS) and(bicyclo[2.2.1]hept-5-en-2-yl)trimethoxysilane (BCHTMS).

TABLE 1 Alkenylalkoxysilane compound Reaction time 1 VTMS  3 minutes 2ATMS 15 minutes 3 OTMS  6 hours 4 BCHTMS  1 day

The hydrolysis time was measured depending on the alkenylalkoxysilane.The time required for the surface modification of silica is determinedby the hydrolysis time.

Preparation of Functional Reinforcing Filler Using AlkenylsilanolObtained by Hydrolyzing Alkenylalkoxysilane Compound Example 1

24.0 mmol (3.56 g) of vinyltrimethoxysilane (VTMS) was added to 3.56 gof a 1% acetic acid aqueous solution (pH ˜3.5) in a 25-mL flask. Afterstirring for 3 minutes at room temperature, a transparent vinylsilanolsolution was obtained. The hydrolyzed vinylsilanol solution was added toa slurry containing 60 g of silica (Z115GR, Rhodia Silica) and 150 g ofmethanol, and the mixture was stirred at room temperature for 10minutes. Then, after evaporating the solvent and volatile materialsusing a rotary vacuum evaporator, residual solid particles weredehydration condensed in an oven at 130° C. for 8 hours to preparesilica (hydrophobic, highly dispersible functional reinforcing filler)surface-modified with the vinyl group.

Example 2

24.0 mmol (3.89 g) of allyltrimethoxysilane (ATMS) was added to 3.89 gof a 1% acetic acid aqueous solution (pH ˜3.5) in a 25-mL flask. Afterstirring for 15 minutes at room temperature, a transparent allylsilanolsolution was obtained. The hydrolyzed allylsilanol solution was added toa slurry containing 60 g of silica (Z115GR, Rhodia Silica) and 150 g ofmethanol, and the mixture was stirred at room temperature for 10minutes. Then, after evaporating the solvent and volatile materialsusing a rotary vacuum evaporator, residual solid particles weredehydration condensed in an oven at 130° C. for 8 hours to preparesilica (hydrophobic, highly dispersible functional reinforcing filler)surface-modified with the allyl group.

Example 3

24.0 mmol (5.58 g) of 7-octenyltrimethoxysilane (OTMS) was added to 5.58g of a 1% acetic acid aqueous solution (pH ˜3.5) in a 25-mL flask. Afterstirring for 6 hours at room temperature, a transparent 7-octenylsilanolsolution was obtained. The hydrolyzed 7-octenylsilanol solution wasadded to a slurry containing 60 g of silica (Z115GR, Rhodia Silica) and150 g of methanol, and the mixture was stirred at room temperature for10 minutes. Then, after evaporating the solvent and volatile materialsusing a rotary vacuum evaporator, residual solid particles weredehydration condensed in an oven at 130° C. for 8 hours to preparesilica (hydrophobic, highly dispersible functional reinforcing filler)surface-modified with the 7-octenyl group.

Example 4

24.0 mmol (5.14 g) of (bicyclo[2.2.1]hept-5-en-2-yl)trimethoxysilane(BCHTMS) was added to 5.14 g of a 1% acetic acid aqueous solution (pH˜3.5) in a 25-mL flask. After stirring for 24 hours at room temperature,a transparent (bicyclo[2.2.1]hept-5-en-2-yl)trisilanol solution wasobtained. The hydrolyzed (bicyclo[2.2.1]hept-5-en-2-yl)trisilanolsolution was added to a slurry containing 60 g of silica (Z115GR, RhodiaSilica) and 150 g of methanol, and the mixture was stirred at roomtemperature for 10 minutes. Then, after evaporating the solvent andvolatile materials using a rotary vacuum evaporator, residual solidparticles were dehydration condensed in an oven at 130° C. for 8 hoursto prepare silica (hydrophobic, highly dispersible functionalreinforcing filler) surface-modified with thebicyclo[2.2.1]hept-5-en-2-yl group.

Examples 5-6

Surface-modified silica (hydrophobic, highly dispersible functionalreinforcing filler) was prepared in the same manner as in Example 2,except for using 36.0 mmol (5.91 g, Example 4) or 48.0 mmol (7.88 g,Example 5) of allyltrimethoxysilane.

Example 7

24.0 mmol (3.89 g) of allyltrimethoxysilane (ATMS) was added to 3.89 gof a 1% acetic acid aqueous solution (pH ˜3.5) in a 25-mL flask. Afterstirring for 15 minutes at room temperature, a transparent allylsilanolsolution was obtained. After adding 3 g ofbis[(triethoxysilyl)propyl]tetrasulfide (TESPT) and 3 g of a 1% aceticacid aqueous solution to a slurry containing 60 g of silica (Z115GR,Rhodia Silica) and 150 g of methanol, the mixture was stirred at about65° C. for 2 hours and then cooled to room temperature. Subsequently,after adding the hydrolyzed allylsilanol solution, the mixture wasstirred at room temperature for 10 minutes. Then, after evaporating thesolvent and volatile materials using a rotary vacuum evaporator,residual solid particles were dehydration condensed in an oven at 130°C. for 8 hours to prepare silica (hydrophobic, highly dispersiblefunctional reinforcing filler) surface-modified with the allyl group andthe bis[polyhydroxysilyl)propyl]tetrasulfide group.

Example 8

24.0 mmol (3.89 g) of allyltrimethoxysilane (ATMS) was added to 3.89 gof a 1% acetic acid aqueous solution (pH ˜3.5) in a 25-mL flask. Afterstirring for 15 minutes at room temperature, a transparent allylsilanolsolution was obtained. After adding 3 g of3-mercaptopropyltrimethoxysilane (MPTMS) and 3 g of a 1% acetic acidaqueous solution to a slurry containing 60 g of silica (Z115GR, RhodiaSilica) and 150 g of methanol, the mixture was stirred at about 65° C.for 2 hours and then cooled to room temperature. Subsequently, afteradding the hydrolyzed allylsilanol solution, the mixture was stirred atroom temperature for 10 minutes. Then, after evaporating the solvent andvolatile materials using a rotary vacuum evaporator, residual solidparticles were dehydration condensed in an oven at 130° C. for 8 hoursto prepare silica (hydrophobic, highly dispersible functionalreinforcing filler) surface-modified with the allyl group and the3-mercaptopropyl group.

Simultaneous Preparation of Alkenylsilanol and Functional ReinforcingFiller Example 9

A suspension including 60 g of silica (Z115GR, Rhodia Silica), 150 g ofmethanol, 3.89 g of allyltrimethoxysilane and 3.89 g of a 1% acetic acidaqueous solution was stirred at room temperature for 10 minutes. Then,after evaporating volatile materials using a rotary vacuum evaporator,residual solid particles were heated in an oven at 130° C. for 8 hoursto prepare surface-modified silica (functional reinforcing filler).

Preparation of Rubber Sample Using Hydrophobic, Highly DispersibleFunctional Reinforcing Filler Preparation Example

[Standard Mixing Protocol]

Test samples of rubber compositions including the silica prepared inExamples t were prepared according to the standard mixing protocol shownin Table 2. The components were mixed using a Haake mixer (Rheocord9000) at 140° C. to prepare the test samples.

TABLE 2 Amount Adding time Rotor speed (parts by weight) (min) (rpm)First pass SSBR⁽¹⁾ 100 0 60 BR⁽²⁾ 30 0 Filler 70 2 Zinc oxide⁽³⁾ 3 0.5Stearic acid⁽⁴⁾ 2 0.5 Wax⁽⁵⁾ 2 0.5 3C⁽⁶⁾ 3 0.5 Sweep 3 Second passProducts of first pass All 7 15.3 Sulfur⁽⁷⁾ 1.7 CZ⁽⁸⁾ 2 DPG⁽⁹⁾ 0.6⁽¹⁾SSBR: solution styrene-butadiene rubber (Sol6450SL, KumhoPetrochemical) ⁽²⁾BR: butadiene rubber (KBR-01, Kumho Petrochemical)⁽³⁾Zinc oxide: ZnO#2 (Hanil Zinc) ⁽⁴⁾Stearic acid: STAcid (LG Chem)⁽⁵⁾Wax: P-Wax (Nippon Seiro) ⁽⁶⁾N-isopropyl-N′-phenylenediamine (3C,Samwon) ⁽⁷⁾Sulfur: SP-325 (Miwon Commercial) ⁽⁸⁾CZ:N-cyclohexylbenzothoazylsulfenamide (SAMACCZ, Samwon) ⁽⁹⁾DPG:diphenylguanidine

Preparation Example 1

A rubber sample was prepared using the hydrophobic, highly dispersiblefunctional reinforcing filler prepared in Example 1 according to thestandard mixing protocol of Table 2. The composition of the rubbersample is shown in Table 3.

Preparation Example 2

A rubber sample was prepared using the hydrophobic, highly dispersiblefunctional reinforcing filler prepared in Example 2 according to thestandard mixing protocol of Table 2. The composition of the rubbersample is shown in Table 3.

Preparation Example 3

A rubber sample was prepared using the hydrophobic, highly dispersiblefunctional reinforcing filler prepared in Example 3 according to thestandard mixing protocol of Table 2. The composition of the rubbersample is shown in Table 3.

Preparation Example 4

A rubber sample was prepared using the hydrophobic, highly dispersiblefunctional reinforcing filler prepared in Example 4 according to thestandard mixing protocol of Table 2. The composition of the rubbersample is shown in Table 3.

Preparation Examples 5-6

Rubber samples were prepared using the hydrophobic, highly dispersiblefunctional reinforcing fillers prepared in Examples 5-6 according to thestandard mixing protocol of Table 2. The composition of the rubbersample is shown in Table 3.

Preparation Examples 7-8

Rubber samples were prepared using the hydrophobic, highly dispersiblefunctional reinforcing fillers prepared in Example 2 according to thestandard mixing protocol of Table 2. The composition of the rubbersample is shown in Table 3.

Preparation Example 9

A rubber sample was prepared using the hydrophobic, highly dispersiblefunctional reinforcing filler prepared in Example 7 according to thestandard mixing protocol of Table 2. The composition of the rubbersample is shown in Table 3.

Preparation Example 10

A rubber sample was prepared using the hydrophobic, highly dispersiblefunctional reinforcing filler prepared in Example 8 according to thestandard mixing protocol of Table 2. The composition of the rubbersample is shown in Table 3.

Preparation Example 11

A rubber sample was prepared using the hydrophobic, highly dispersiblefunctional reinforcing filler prepared in Example 9 according to thestandard mixing protocol of Table 2. The composition of the rubbersample is shown in Table 3.

Comparative Preparation Examples 1-6

Rubber samples were prepared by simply mixing sulfur-freeallyltrimethoxysilane (ATMS) with non-surface-treated silica at 140° C.(Comparative Preparation Examples 1-2), using a sulfur-free couplingagent 3-mercaptopropyltrimethoxysilane (MPTMS) and non-surface-treatedsilica (Comparative Preparation Examples 3-4), or using a coupling agentbis[(triethoxysilyl)propyl]tetrasulfide (TESPT) and non-surface-treatedsilica (Comparative Preparation Examples 5-6). The composition of therubber samples is shown in Table 3.

TABLE 3 Preparation Examples Comparative Preparation Examples (parts byweight) (parts by weight) 1-6 7 8 9-11 1 2 3 4 5 6 SSBR 100 100 100 100100  100  100  100  100  100  BR 30 30 30 30 30  30  30  30  30  30 Filler Surface-modified 70 70 70 70 — — — — — — silica Non-surface- — —— — 65.4 65.4 64.1 64.1 64.4 64.4 modified silica⁽¹⁾ Coupling agent — —— —   4.6⁽²⁾   4.6⁽²⁾   5.9⁽³⁾   5.9⁽³⁾   5.6⁽⁴⁾   5.6⁽⁴⁾ Zinc oxide 3 33 3 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 2 2 2 2 Wax 2 2 2 2 2 2 2 2 2 23C 3 3 3 3 3 3 3 3 3 3 Sulfur 1.7 3.0 5.0 1.7  1.7  3.0  1.7  3.0  1.7 3.0 CZ 2 2 2 2 2 2 2 2 2 2 DPG 0.6 0.6 0.6 0.6  0.6  0.6  0.6  0.6  0.6 0.6 ⁽¹⁾Silica: Z115GR (Rhodia Silica) ⁽²⁾ATMS: TCD ⁽³⁾MPTMS: TCD⁽⁴⁾TESPT: Si69 (Evonik)

Test Example 2 Physical Properties of Rubber Sample

Physical properties of the rubber samples prepared in PreparationExamples 1-10 and Comparative Preparation Examples 1-6 were measured.The result is shown in Table 4.

The samples were cured for the T90 time according to ASTM D-2094, i.e.the time during which 90% of vulcanization is completed, plus additional5 minutes at 150° C. under a pressure of 2,000 lb/int. Physicalproperties of the samples were measured using the test method Aaccording to ASTM D412-98a. Extension rate, tensile stress and moduluswere measured using the Lloyd instruments (LRX Plus, Ametek, Inc.). InTable 4, TS2 indicates the scorch time, or the initial curing time, ofrubber.

TABLE 4 Preparation Examples Comparative Preparation Examples 1 2 3 4 56 7 8 9 10 11 1 2 3 4 5 6 Scorch time 15.1 17.0 16.6 16.2 16.5 14.1 16.813.7 12.2 10.9 16.9 14.1 14.8 1.1 1.3 7.5 5.5 (TS2) Vulcanization 18.921.8 20.1 20.0 22.6 17.4 22.5 32.0 16.4 15.5 21.0 16.7 23.4 7.9 8.5 13.113.1 time (T90) Tensile 17.3 17.9 17.3 17.5 18.0 18.2 19.3 19.6 19.518.9 17.8 16.9 17.2 11.0 10.8 15.9 15.0 strength (MPa) 300% modulus 13.915.1 14.1 14.2 16.1 17.3 17.8 18.2 18.1 17.9 13.9 15.5 16.2 12.3 11.412.6 12.2 (MPa)

As seen from Table 4, the rubber samples prepared in PreparationExamples 1-4 using the silica surface-modified with thealkenylalkoxysilane exhibited longer scorch time and vulcanization time,and hence better processability and higher tensile strength and 300%modulus, than the rubber samples prepared in Comparative PreparationExamples 3-6 using the sulfur-containing silane coupling agent. Amongthem, the rubber sample prepared in Preparation Example 2 using thesilica surface-modified with allyltrimethoxysilane showed the bestresult as a reinforcing filler with satisfactory scorch time,vulcanization time, tensile strength and 300% modulus. Comparison ofPreparation Examples 5 and 6 reveals that tensile strength and 300%modulus can be improved by increasing the amount ofallyltrimethoxysilane. Preparation Examples 7 and 8 show that thetensile strength and modulus can be significantly improved by addingsulfur to Preparation Example 2, without having to add the expensivecoupling agent as in Preparation Examples 5-6. This is because thesulfur that has been uniformly dispersed in the rubber mixture reactswith the allyl group of the coupling agent, thereby facilitating therubber-coupling agent-silica bonding. Also, it was identified throughPreparation Examples 9 and 10 that physical properties can be greatlyimproved by modifying the surface using the sulfur-containing TESPT orMPTMS. In Preparation Example 11, wherein allylsilanepolyol and silicawere surface-modified simultaneously using allyltrimethoxysilane, asimilar result was obtained as in Preparation Example 2.

Preparation Example 2 wherein the silica surface-modified withallyltrimethoxysilane was used showed better physical properties ascompared to Comparative Preparation Example 1 wherein silane and sulfurwere simply mixed with the same amount. Comparative Preparation Example1 showed slightly improved physical properties as compared toComparative Preparation Example 2, revealing that the addition of sulfurwhen mixing allyltrimethoxysilane with silica rubber can provideimproved physical properties. In Comparative Preparation Examples 3-6,wherein sulfur-containing MPTMS or TESPT was used as the coupling agent,further addition of sulfur did not lead to improved physical properties.

Test Example 3 Dynamic Properties of Rubber Sample

Dynamic properties of the rubber samples prepared in PreparationExamples and Comparative Preparation Examples were measured. The resultis shown in Tables 5 and 6.

TABLE 5 Preparation Examples 1 2 3 4 5 6 7 8 9 10 11 Tan δ (0° C.) 0.1990.205 0.203 0.200 0.196 0.206 0.215 0.217 0.207 0.207 0.203 Tan δ (60°C.) 0.075 0.069 0.077 0.075 0.060 0.051 0.053 0.050 0.049 0.052 0.068

TABLE 6 Comparative Preparation Examples 1 2 3 4 5 6 Tan δ (0° C.) 0.2050.205 0.155 0.165 0.162 0.187 Tan δ (60° C.) 0.069 0.061 0.066 0.0610.059 0.056

Since Preparation Examples show higher tan δ (0° C.) and lower tan δ(60° C.) values as compared to Comparative Preparation Examples,improvement in braking performance and low rotational resistance areexpected. Especially, Preparation Examples 7-10 exhibited high tan δ (0°C.) values as well as low tan δ (60° C.) values. This may be due to theaddition of sulfur or the sulfur-containing coupling agent to the rubbermixture of silica surface-modified with allyltrimethoxysilane.

Since the functional reinforcing filler of the present invention has afunctional group having a double bond, it has good reactivity forstyrene-butadiene rubber and sulfur. Thus, when used as a functionalreinforcing filler in the manufacture of rubber, it allows improvementof physical properties through adjustment of the addition amount ofsulfur without additional use of the coupling agent. In addition,because of superior hydrolysis reactivity, the problem of alcohol can besolved and a rubber mixture with long scorch time can be prepared. Inparticular, when the functional reinforcing filler of the presentinvention is used in the manufacture of tires, improvement in modulus,tensile strength, rotational resistance and wet traction performance canbe expected.

The present invention has been described in detail with reference tospecific embodiments thereof. However, it will be appreciated by thoseskilled in the art that various changes and modifications may be made inthese embodiments without departing from the principles and spirit ofthe invention, the scope of which is defined in the appended claims andtheir equivalents.

What is claimed is:
 1. A method for preparing a functional reinforcingfiller, comprising: preparing an alkenylsilanol solution by hydrolyzingan alkenylalkoxysilane compound represented by Chemical Formula 1;preparing a suspension by mixing the alkenylsilanol solution withinorganic particles in one or more solvent selected from alcohol andwater; preparing molecular film coated inorganic particles by removingthe solvent from the suspension through evaporation; and heating themolecular film coated inorganic particles to induce dehydrationcondensation:R—SiX¹X²X³  (1) wherein R is C₂-C₁₈ alkenyl or C₅-C₁₈ cycloalkenyl, andeach of X¹, X² and X³, which are the same or different, is C₁-C₁₈ alkyl,C₁-C₁₈ alkoxy, C₆-C₁₈ aryl or C₆-C₁₈ aromatic alkoxy, with the provisothat at least one of X¹, X² and X³ is C₁-C₁₈ alkoxy or C₆-C₁₈ aromaticalkoxy.
 2. The method according to claim 1, wherein the hydrolysis isperformed at pH 2.5 to 5.0.
 3. The method according to claim 1, wherein,in said preparing the suspension, a coupling agent selected frombis[(trimethoxysilyl)propyl]tetrasulfide (TMSPT),bis[(triethoxysilyl)propyl]tetrasulfide (TESPT),3-mercaptopropyltrimethoxysilane (MPTMS) and3-mercaptopropyltriethoxysilane (MPTES) is added.
 4. The methodaccording to claim 1, wherein the inorganic particles are silica.
 5. Themethod according to claim 1, wherein the dehydration condensation isperformed at 100 to 150° C.
 6. A method for preparing a functionalreinforcing filler, comprising: preparing a suspension by mixing analkenylalkoxysilane compound represented by Chemical Formula 1 withinorganic particles in one or more solvent selected from alcohol andwater; removing the solvent from the suspension through evaporation; andheating the inorganic particles to induce dehydration condensation andthereby modifying the surface of the inorganic particles:R—SiX¹X²X³  (1) wherein R is C₂-C₁₈ alkenyl or C₅-C₁₈ cycloalkenyl, andeach of X¹, X² and X³, which are the same or different, is C₁-C₁₈ alkyl,C₁-C₁₅ alkoxy, C₆-C₁₈ aryl or C₆-C₁₈ aromatic alkoxy, with the provisothat at least one of X¹, X² and X³ is C₁-C₁₈ alkoxy or C₆-C₁₈ aromaticalkoxy.
 7. The method according to claim 6, wherein the suspension isprepared by mixing at pH 2.5 to 5.0.
 8. The method according to claim 6,wherein a coupling agent selected frombis[(trimethoxysilyl)propyl]tetrasulfide (TMSPT),bis[(triethoxysilyl)propyl]tetrasulfide (TESPT),3-mercaptopropyltrimethoxysilane (MPTMS) and3-mercaptopropyltriethoxysilane (MPTES) is added.